Final answer:
The chemical driving force on Na+ includes both a concentration gradient and an electrical gradient, combining to form an electrochemical gradient that typically favors the inward movement of Na+ ions into the cell.
Step-by-step explanation:
The chemical driving force on Na+ (sodium ions) in a situation where multiple ion species are present would indeed include influences from both the concentration and electrical gradients. Living cells typically have a higher internal concentration of K+ (potassium ions) and a lower concentration of Na+ compared to the extracellular fluid. Since cells are also typically negatively charged on the inside, they experience an electrical gradient that attracts positively charged ions like Na+ into the cell.
This combination of the concentration gradient, which drives Na+ into the cell due to its lower internal concentration, and the electrical gradient, which also drives Na+ into the cell due to the cell's negative charge, creates what is called an electrochemical gradient. Moreover, while these gradients favor the inward movement of Na+, they affect other ions differently, such as K+, where the concentration gradient favors its movement out of the cell.